US1944987A - Turbine - Google Patents

Description

Jan. 3o, 1934. F LJUNGSTROM 1,944,987`

TURBINE Filed June 16, 1952 Z'Sheets- Shet l if j? -lNvENToR ATTORNEYS Jan. 30, 1934. V F JUNGSTRM 1,944,987

TURBINE Filed June 16. 1932 2 Sheets-Sheet 2 MM Ww ATTORN EYS Patented Jan. 30, 1934 UNITED STATES PATENT OFFICE TURBINE Application June 16, 1932, Serial No. 617,653, and in Sweden July 3, 1931 8 Claims.

My present invention relates to steam turbines of the type in which the blades of the last blade rim reckoned in their longitudinal direction have a more or less radial extension, and more particularly to steam turbines having outwardly arc-bent blades secured at both ends, said blades on rotation adjusting themselves in the form of catenary lines by the action of centrifugal force. Turbines of this type are disclosed in my copending applications Vfor Letters Patent Serial Nos. 386, 241 of August 16th, 1929 and 561,565 of September 8th, 1931.

As proposed in said latter patent application the blades may be manufactured of thin sheet `metal permitting very high peripheral speeds and very large outlet areas in turbines of high rates of revolution. Turbines of the type referred to can, for instance, be built for an output of 100,000 kw. and a speed of 3000 revolutions per minute.

The principal object of my invention is to provide a turbine of the type described in which the discharge loss, that is the loss due to the outflow velocity of the exhaust steam from the 'last blade rim in relation to the surroundings, is utilized to effect an elevated vacuum around said blade rim in order to regain a considerable part of said discharge loss.

A further object of my invention is to provide a steam turbine of the type referred to having an exhaust chamber of such a shape as to permit an undisturbed formation of a rotating steam ring around the last blade ring of the steam turbine, no stationary part of the turbine falling within the space required for said rotating steam ring.

Still another object of my invention is to` provide a steam turbine of the type described in which protecting shields are provided in the turbine casing in order to prevent steam existing 4:0l within the turbine casing, but not rotating around the axis of rotation of the turbine, from disturbing or interfering with the formation of said rotating steam ring.

The invention will be more fully described with reference to the accompanying drawings in which connection also other features characterizing the invention will be set forth.

In the drawings:-

Fig. lis an elevation in part in section of a steam turbine embodying the invention.

Fig. 2 is a similar view of a slight modification of Fig. 1, and

vlig.y 3 is a diagrammatic end view, partly in section onr the center line of Fig. 1.

In the drawings a designates the exhaust (Cl. 25E-16.5)

chamber of the turbine connected with the condenser b. The last blade rim e of the turbine is designed in accordance with my above mentioned previous applications for Letters Patent, thus consisting of outwardly bent blades secured at both ends and formed or thin sheet metal, said blades on rotation adjusting themselves in the form of catenary lines by the action of centrifugal force. Thus said blades have a relatively large radial extension as measured from the 05 secant at the base of the blades to the crest of their arcs. In turbines of this type the discharge loss may be very great, the steam leaving the outlet rim e at a speed of rotation of for instance 200 meters per second and at a radial speed of 'l0 for instance 100 meters per second. VThe outow of the steam may be conceived as taking place in the form of a ring of steam c rotating around the blade system, within which ring a permanent interchange of steam takes place in the direction from within outwards. This rotating steam ring c is evidently subjected to the influence of centrifugal force with the result that the pressure tends to rise within same in the direction from the centre outwards approximately in the 8.0 same manner as in centrifugal pumps. This increase of pressure is facilitated by the radial speed component of the flow of the steam being` decreased according as, during the rotation within the ring, the steam forms an extended area from within outwards. The steam ring c may be conceived to be limited by the lines d and f, said lines together with the contour line e which, as mentioned above, designates the last blade rim of the turbine indicating the body of rotation of the steam. Lines f designate funnel-shaped shields arranged concentrically around the axis of rotation of the turbine, whereas d is a conceived as a limiting line which actually only designates a certain degree of decrease of speed and extension of area of the steam leaving the last blade rim e.

By the rotation within the steam ring c there is, as mentioned above, a tendency to an increase in pressure arising outwardly towards the limiting line d. Assuming that a certain back pressure is prevailing in the exhaust chamber a of the turbine amounting to, for instance, 0.04 atmospheres, no higher pressure can, evidently, occur within the steam ring c, that is the pressure at said limiting line d cannot exceed this value. As, however, on account of the rotation an increase of pressure arises during the passage of the steam between e and d, this will result in a vacuum being created at e lower than the pressure in the exhaust chamber a, that is lower than 0.04 atmospheres, for instance amounting to 0.01 atmospheres. As the pressure at the points g outside the limiting shields f is the same as in the main part of the turbine exhaust a, thus amounting to 0.04 atmospheres, different pressures will prevail on opposite sides of the shields f, that is a lower pressure along the line e and a higher pressure outside said shields f.

As apparent from the drawings no stationary members belonging to the turbine exist within the rotating steam ring c, which members could disturbingly influence the formation of such a ring. The shields f constitute means to ensure an undisturbed rotation of the steam ring c, said shields preventing steam existing within the turbine casing but not taking part in the rotation from disturbingly interfering with the body of rotating steam. Thereby the rotation within the steam ring c will have the possibility of developing in a rational and eiiective manner, the velocity which represents the discharge loss being to the greatest possible degree utilized for creating an increased fall of heat within the last blade rim or a lower back pressure than that prevailing in the other portions of the turbine outlet a.

In the embodiments shown in the drawings the steam turbine is or" the type having outwardly arc-bent blades secured at both ends and having at said ends an essentially radial direction. As apparent from the two iigures the shields f extend radially outwards from the inner ends of the blades of the outlet blade rim e, permitting lby the rotation of the steam a pressure increase from within outwards.

The general idea of regaining the discharge loss is not new, but constructions for this purpose hitherto known are not of the kind permitfting an undisturbed rotation of said steam ring c. It has been proposed to arrange a diiusor in the turbine exhaust, said diiusor being divided into sections creating each a vacuum for utilizing the outow velocity by decrease of speed within the steam flowing through the diiierent sections. However, in this case the diferent partitions and stays of the diiiusor will prevent or interfere with the formation of a rotating steam ring, and moreover the steam will enter the sections of the diiusor at variable angles depending on the load on the turbine and the vacuum in the turbine exhaust. Thereby the action or the diffuser will be reduced or wholly destroyed, it being, as well known, of Very great importance that .a steam current in which a speed is to be transformed into pressure by area expansion enter the so called diffusor funnel in correct direction, because if the steam jet enters in a considerably oblique direction the jet will follow the one wall of the funnel causing no compression of the steam.

Contrary to that the structure according to my present invention will, independent of different loads or diierent vacua in the turbine exhaust, always cause a centrifugal compression of the steam in the rotating steam ring and also a compression on account of the change of the radial speed component of the steam current due to area extension.

What I claim isz- 1. In a steam turbine, in combination with a discharge rotor provided with a blade rim including blades of relatively large radial extension as measured from the secant at the base to the crest of the blades, means providing a disblade rim composed of blades having a curved periphery and attached at their bases to said rotor, means providing a discharge or outlet chamber entirely surrounding said rotor and forming therewith an unobstructed annular space which embraces said blade rim throughout the curved periphery of said blades, whereby the steam ilowing from all portions of the periphery of said blades may form a steam ring of constant cross sectional area and free to rotate with said rotor, and means diverging from the base of said blades and defining laterally said rotating steam ring.

3. In a turbine, in combination with a discharge rotor having a radially extended blade rim composed or iiexible blades which assume the form or" catenaries under the influence of centriiugal force and which are attached at their opposite ends to said rotor, means providing a discharge or outlet chamber entirely surrounding said rotor and forming therewith an unobstructed annular' space which embraces said blade rim throughout the periphery of said blades, whereby all of the steam flowing from said blades may form a steam ring of constant cross sectional area freely rotating with said rotor, and means extending divergently outward from adjacency to the ends of said blades for dening laterally said 15 all parts of the periphery of said blades to formv a freely rotating steam ring of substantially uniform cross section wherein an increase in steam pressure with decrease of velocity is afforded for the steam as it leaves said blades, and means extending outwardly from adjacency to the periphery of said rotor for dening laterally said rotating steam ring.

5. In a steam turbine, in combination with a discharge rotor provided with a blade rim includ-- ing blades of relatively large radial extension as measured from the 'secant at the base to the crest of the blades, means providing a discharge or outlet chamber entirely surrounding said rotor and providing an unobstructed annular space embracing the entire blade rim, wherein the discharged 1 steam may form a freely rotating steam ring of constant cross sectional area and which is dened at its inner margin by the total periphery of said radially extended blades, and stationary shields within said discharge or outlet chamber extending outwardly from the base of saidblades for preventing steam in said chamber from interferring With the formation of the rotating steam ring.

6. n a turbine, in combination with a discharge rotor provided with a radially extended blade rim composed of blades having a curved periphery and attached at their bases to said rotor, means providing a discharge or outlet chamber entirely surrounding said rotor and forming therewith an unobstructed annular space which embraces said blade rim throughout the curved periphery of said blades, whereby the steam owing from all portions of the periphery of said blades may form a steam ring' of constant cross sectional area and free to rotate with said rotor, and stationary shields within said discharge or outlet chamber diverging from the base of said blades for preventing steam in said chamber from interfering with the formation of the rotating steam ring.

7. In a turbine, in combination with a discharge rotor having a radially extended blade rim composed of exible blades which assume the form of catenaries under the influence of centrifugal force and which are attached at their opposite ends to said rotor, means providing a discharge or outlet chamber entirely surrounding said rotor and forming therewith an unobstructed annular space which embraces said blade rim throughout the periphery of said blades, whereby all of the steam owing from said blades may form a steam ring of constant cross sectional area freely rotating with said rotor, and stationary shields within said discharge or outlet chamber extending di-v vergently outward from adjacency to the ends of said blades for preventing steam in said chamber from interfering with the formation of the rotating steam ring.

8. In a steam turbine, in combination with a discharge rotor having blades which extend outwardly through a substantially radial extent from the periphery of the rotor and which have curved peripheries, means providing a discharge or outlet chamber entirely surrounding said rotor and forming an unobstructed annular space entirely embracing the curved peripheries of said blades and into which the steam may flow from all parts of the periphery of said blades to form a freely rotating steam ring of substantially uniform cross section wherein an increase in steam pressure with decrease of velocity is aorded for the steam as it leaves said blades, and stationary shields within said discharge or outlet chamber extending outwardly from adjacency to the periphery of said rotor for preventing steam in said chamber from interfering with the formation of the rotating steam ring.

FREDRIK LJtJNGsTnM.

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